Self dressing, mildly abrasive coating for clearance control

Abstract

An abrasive coating for rotor shafts that interact with cantilevered vanes to form an abradable air seal in a turbine engine. The abrasive coating including a metal bond coat layer on the rotor shaft, and an abrasive top coating bond coat layer for contact with vanes during operation of the rotor shaft, the abrasive coating including a plurality of abrasive grit particles in a matrix. the abrasive grit particles are selected from the group consisting of cubic boron nitride (CBN), zirconia, alumina, silicon carbide, diamond and mixtures thereof.

1 . An abrasive coating for a rotor shaft, the abrasive coating comprising:
 a metal bond coat layer on the rotor shaft; and   an abrasive coating on the bond layer for contact with vanes during operation of the rotor shaft, the abrasive coating including a plurality of grit particles.   
     
     
         2 . The abrasive coating of  claim 1 , wherein the metal bond coating ranges in thickness from about 3 mils to about 7 mils (about 76 to about 178 microns). 
     
     
         3 . The abrasive coating of  claim 1 , wherein the metal bond coating is formed of MCrAlY, where M is nickel, iron, cobalt or mixtures thereof. 
     
     
         4 . The abrasive coating of  claim 1 , wherein the plurality of grit particles are in a matrix of hexagonal boron nitride, Ni, Cr, MCrAlY and mixtures thereof, and wherein the metal (M) can be nickel, cobalt, iron or mixtures thereof. 
     
     
         5 . The abrasive coating of  claim 4 , wherein the abrasive grit particles are selected from the group consisting of cubic boron nitride (CBN), zirconia, alumina, silicon carbide, diamond and mixtures thereof. 
     
     
         6 . The abrasive coating of  claim 4 , wherein the abrasive grit coating has a particle size ranging from about 25 microns to about 75 microns. 
     
     
         7 . The abrasive coating of  claim 1 , wherein the abrasive grit coating ranges in thickness from about 3 mils to about 30 mils (about 76 to about 763 microns). 
     
     
         8 . The abrasive coating of  claim 1 , which further includes a ceramic layer between the bond layer and the abrasive layer, the ceramic layer having a thickness ranges from about 7 mils to about 12 mils about 178 to about 305 microns). 
     
     
         9 . An abrasive coating for rotor shafts, the abrasive coating comprising:
 a metal bond coat layer on the rotor shaft ranging in thickness from about 3 mils to about 7 mils (about 76.2 to about 177.8 microns); and   an abrasive grit layer overlying the metal bond layer for contact with cantilevered vanes during operation of the rotor shaft to form an abradable air seal, the abrasive grit layer having a thickness from about 3 mils to about 7 mils (about 76 to about 178 microns).   
     
     
         10 . The abrasive coating of  claim 9 , wherein the grit particles are in a matrix of hBN, Ni, Cr, MCrAlY and mixtures thereof, and wherein the metal (M) is nickel, cobalt, iron or mixtures thereof. 
     
     
         11 . The abrasive coating of  claim 10 , wherein the abrasive grit particles are selected from the group consisting of cubic boron nitride (CBN), zirconia, alumina, silicon carbide, diamond and mixtures thereof. 
     
     
         12 . The abrasive coating of  claim 11 , wherein the grit coating has a particle size ranging from about 25 microns to about 75 microns and wherein the abrasive grit coating ranges in thickness from about 3 mils to about 30 mils (about 76 to about 763 microns). 
     
     
         13 . The abrasive coating of  claim 9 , wherein the metal bond coating is formed of MCrAlY, where is nickel or cobalt, and the alloying elements are chromium (Cr), aluminum (Al) and yttrium (Y). 
     
     
         14 . The abrasive coating of  claim 9 , which further includes a ceramic layer between the metal bond layer and the abrasive grit layer, the ceramic layer having a thickness of from about 7 mils to about 12 mils (about 178 to about 305 microns). 
     
     
         15 . A compressor for a gas turbine engine comprising:
 an airfoil with a radial outward end and an airfoil tip at a radial inward end;   a seal member adjacent to the radial inward end of the airfoil wherein one of the seal member and airfoil tip is coated with an abrasive coating including an abrasive grit layer in a matrix and the other is bare metal.   
     
     
         16 . The compressor of  claim 15 , wherein the abrasive grit layer includes grit particles selected from the group consisting of cubic boron nitride (CBN), zirconia, alumina, silicon carbide, diamond and mixtures thereof. 
     
     
         17 . The compressor of  claim 15 , wherein the abrasive grit coating ranges in thickness from about 3 mils to about 30 mils (about 76 to about 763 microns). 
     
     
         18 . The compressor of  claim 16 , wherein the abrasive grit particles are in a matrix of hexagonal boron nitride, Ni, Cr, MCrAlY and mixtures thereof, and wherein the metal (M) can be nickel, cobalt, iron or mixtures thereof. 
     
     
         19 . The compressor of  claim 18 , wherein the abrasive grit coating has a particle size ranging from about 25 microns to about 75 microns. 
     
     
         20 . The compressor of  claim 15 , which further includes a metal bond layer on the seal member and the abrasive grit coating is applied to the metal bond layer, the metal bond layer being formed of MCrAlY, where M is nickel, iron, cobalt or mixtures thereof. 
     
     
         21 . The compressor of  claim 20 , which further includes a ceramic layer between the metal bond layer and the grit layer, the ceramic layer having a thickness of from about 7 mils to about 12 mils (about 178 to about 305 microns).